Young Sasuke Uchiha was gone for so long during his betrayal that he was considered a rouge ninja by everyone in his home village, including the young girls that once "loved" him. Even ms. Sakura Haruno.
So when he came back & apologized for his wrongs, alot of people weren't ready to forgive him, & never did. Young Sakura was so bitter about his re-arrival, that she requested he be exxecuted by lady hokage, however, Tsunade welcomed him back & let him live normally. Since none of the young girls would talk to him like they once dreamed to do, he became desperate & had to marry his long time stalker, Karin. He didn't love her any more than he loved the thought of being forever alone, so he stayed with her & she had his child, a baby boy he named Waruji Uchiha.
When Waruji was born, Sasuke could tell by the look in his eyes he would one day be a powerful ninja, & could maybe even revive his plan to destroy the leaf village once & for all. So he pushed him extremely hard, & basically used him as a weapon. He taught him how to perfect the lightening blade, snake summoning jutsu, & His sharingan by the age of 8. This turned him into a bit of a evil freak, but like the girls did unto Sasuke at his young age, the girls chased after Waruji.
Also like his dad, he had no interest in any of them & just wanted to be strong. He made no friends, & lived only for power. He is very arrogant. This sparked a hatred/rivalry between him & Hinaru. [son of naruto & hinata]
He was assigned to team 1 with his rival Hinaru Uzumaki, & Rock Lei [daughter of Sakura & Lee] Thus, his adventures as a powerful genin began.

an RPC done on MS paint only. Done off of a screen shot of Sasuke Uchiha shippuden.